Increasing speed of digital printers has created a need for matching high speed RIP (Raster Image Processing) systems. An RIP system converts Page Description Language (PDL) data, such as Portable Document Format (PDF) developed by Adobe Systems Inc., or XPS developed by Microsoft Corporation, into pixel data that can be used as input to a digital printer.
Traditionally RIP systems have utilized general purpose processors (CPUs) or custom hardware. Recently, Graphics Processing Units (GPUs), originally designed for 3D rendering applications such as computer games and computer-aided design (CAD), have become very powerful, and provide much higher performance to price ratio than general purpose CPUs. A RIP system built with GPUs may be cheaper than an equivalently performing CPU based system.
There are several existing examples of using GPUs in RIP systems. These existing systems typically comprise a host system containing a CPU, a main memory and one or more GPU cards connected by a peripheral bus, such as PCI-e. Each GPU card contains a graphics processing unit (GPU), a memory and one or more video output interfaces for connecting display devices. In one known GPU-based RIP system, pixels rendered on a GPU are transferred back to host system main memory, where additional colour processing may be performed by a general purpose processor (CPU). In alternative known systems, rendered pixels are transferred from memory associated with a GPU to a printer, via another device connected to a peripheral bus such as, for example, a PCI-e network card. Transferring the pixel data from GPU to main memory and from main memory to another device may require more bandwidth than such a peripheral bus can provide. In this case, the GPUs will not be used to their full potential due to the bottleneck of output bandwidth from the transfer to the CPU or a network interface.
One known system addresses the above problem by compressing pixel data before sending the compressed pixel data across a peripheral bus. Although the data transfer time may be reduced, the extra time required for compression, data transfer and decompression negates the benefit.